1. Technical Field
The present invention relates to a light-emitting element head, a light-emitting element chip, an image forming apparatus and a signal supply method.
2. Related Art
In an electrophotographic image forming apparatus such as a printer, a copy machine or a facsimile machine, an image is formed on a recording paper sheet as follows. Firstly, an electrostatic latent image is formed on a charged photoconductor by causing an optical recording unit to emit light on the basis of image information. Then, the electrostatic latent image is made visible by being developed with toner. Lastly, the toner image is transferred on and fixed to the recording paper sheet. As such an optical recording unit, in addition to an optical-scanning recording unit that performs exposure by laser scanning in a first scan direction using a laser beam, an optical recording unit using the following light-emitting element head has been employed in recent years. This light-emitting element head includes a large number of light-emitting element chips arrayed in a first scan direction, and each light-emitting element chip includes a light-emitting element array formed of light-emitting elements such as light emitting diodes (LEDs) arrayed in a line.
Such a light-emitting element head including a large number of light-emitting element arrays requires as many lighting signals for light-emitting elements as the number of light-emitting element chips. Accordingly, the number of signal bus lines for the light-emitting element heads increases with increase in the number of light-emitting element chips, and this complicates the routing of the signal bus lines. In addition, the larger number of current buffer circuits each having a large current drive capability is required with increase in the number of light-emitting element chips since the lighting signals supply a current to the light-emitting elements.